Injection apparatus

ABSTRACT

In an injection apparatus, a guide screw shaft of a body section (20) and a screw of an operation knob (34) of a movable section (30) allow the movable section (30) to move relative to the body section (20). An ampule (7) is radially inserted into a ampule holding portion (36) of the movable section (30) and temporarily held by means of an elastic blade (36a) and at the same time, a flange (75) of the ampule (70) is inserted into a flange insertion portion (38). When the operation knob (34) is rotated, the movable section (30) moves toward the body section (20) together with the ampule (70). A guide sleeve formed in the body section (20) is inserted into a syringe (77) of the ampule (70). An operation knob (50) is rotated to set the feeding amount of a piston rod, and the operation knob (50) is pressed to perform an injection. When a release button (40) is pressed, the piston rod is returned to an initial position. This construction allows the ampule (70) to be easily mounted on the injection apparatus and the state of medicine in the ampule (70) to be easily seen.

TECHNICAL FIELD

The present invention relates to an injection apparatus, particularly tothe injection apparatus, having an ampule mounted thereon, for manuallygiving an injection of a medicine in the ampule to a patient, and moreparticularly to the injection apparatus which is suitable for an ampulecontaining two-component medicine.

BACKGROUND ART

As an injection apparatus, for giving an injection of a medicine (agent)in an ampule, which is prepared by installing the ampule thereon andmounting a needle on the ampule, and which is operated to inject themedicine in the ampule, a pen-type of injection apparatus as shown inFIG. 1 generally, is mainly used. The injection apparatus 90 of thistype comprises a cylindrical body 92 and a cap 94, and an ampule 95 isinserted into the body 92. A needle 91 is mounted on a front end of theampule 95 projecting from an end of the body 92. Then, a knob 96positioned at a rear end of the cap 94 is operated to set an injectionamount. Then, the knob 96 is pushed toward the needle 91 to move apiston 99 of the ampule 95 through a rod 97. In this manner, a medicine98 is injected to a patient.

In this type of injection apparatus, however, for the installation andremoval of the ampule 95, it is necessary to remove the cap 94 from thebody 92, to insert the ampule 95 into the body 92 or to remove ittherefrom, and, then, to install the cap 94 on the body 92 again. Ittakes time and labor to carry out such an operation, because theengagement between the body 92 and the cap 94 cannot be made favorablyor the cap 94 is separated from the body 92. Thus, the injectionapparatus has a problem in that an operator is inconvenienced whenhandling it.

Further, because the entire ampule 95 is hidden in the injectionapparatus 90, the ampule 95 is not seen from outside or is hard to seeeven though the body 92 has a peep window. Thus, there is a problem inthat the amount of the medicine 98 is hard to see.

DISCLOSURE OF THE INVENTION

The present invention has been developed in view of the above-describedproblems. That is, as a first technical problem to be solved by thepresent invention, the present invention is intended to provide aninjection apparatus on which an ampule can be easily mounted. As asecond technical problem to be solved by the present invention, thepresent invention is intended to allow an ampule installed in theinjection apparatus to be seen easily from outside. In order to solvethe above-described technical problems, the injection apparatus of thepresent invention is constructed as follows.

That is, the injection apparatus, on which an ample having a piston forsealing an agent in a syringe is installed, has piston rod means forpressing the piston of the ampule in an axial direction. The injectionapparatus comprises an ampule holding part and an ampule gripping means.The ampule holding part defines an ampule insertion outer opening whichis expanded in a circumferential direction when the ampule is insertedinto the opening, and defines an ampule insertion space for insertingthe ampule thereinto. In this construction, the outer opening isrestored to its original configuration after the ampule is inserted intothe ampule insertion space, so that the ampule is held by the ampuleholding part temporarily. The ampule gripping means grips the ampule andblocks the movement thereof in both the axial direction and thedirection perpendicular to the axis of the ampule.

In the above construction, in order to mount the ampule on the injectionapparatus, the ampule is inserted into the ampule insertion spacethrough the opening of the injection apparatus in the axial direction(hereinafter, referred to as an "axis") of the ampule or a directionperpendicular thereto. At this time, the opening is expanded by theampule. Because the expanded opening is returned to its originalconfiguration after the ampule is inserted into the ampule insertionspace, the ampule is prevented from falling out of the ampule insertionspace. In other words, the ampule is temporarily held by theampule-holding part. The ampule-gripping means prevents the ampuletemporarily held by the ampule-holding part from moving in both theaxial direction and the direction perpendicular to the axis of theampule. That is, it is unnecessary to disassemble the injectionapparatus or the like upon inserting the ampule into the ampuleinsertion space. The ampule can be mounted on the injection apparatus byinserting the ampule into the ampule insertion space of theampule-holding part and by fixing it by the ampule-gripping means.Because the ampule is temporarily held thereby, it is unnecessary totake particular care of preventing the ampule from falling out of theinjection apparatus.

Accordingly, the ampule with the above construction is easily mounted onthe injection apparatus.

Also, the above-described construction allows the inserted ampule to beviewed easily from outside through the outer opening.

Accordingly, the injection apparatus having the above-describedconstruction allows the mounted ampule to be easily seen from outside.

Preferably, the ampule holding part has a pair of ampule-grippingelastic blades for securing the inserted ampule therebetween. Theopening is defined between the side edges of the pair of ampule-grippingelastic blades and between the front edges thereof, and the ampuleinsertion space is defined by an inner peripheral surface of the pair ofampule-gripping elastic blades. The distance between the side edges ofthe pair of ampule-gripping elastic blades is shorter than an outerdiameter of the syringe of the ampule by a predetermined amount.

In the above-described construction, the ampule is inserted into theampule insertion space through the opening formed between the side edgesof the ampule-holding part in a direction perpendicular to the axis.After the ampule is inserted into the ampule insertion space, a frontend of the ampule on which a needle unit is installed projects to theoutside through the opening formed between the side edges of theampule-holding part. Because the distance between the side edges of thepair of ampule-gripping elastic blades is shorter than the outerdiameter of the syringe of the ampule, the ampule is inserted into theampule insertion space by expanding the ampule-gripping elastic bladesoutward. After insertion, the expanded side edges of the ampule-grippingelastic blades are restored to the original configuration. Thus, themovement of the ampule in the direction perpendicular to the axisthereof is elastically limited. Accordingly, the ampule is held in theampule insertion space temporarily; hence, an accident, such as adropping or falling of the ampule therefrom at time of ampule-mountingoperation, can be prevented.

Preferably, the injection apparatus comprises a body section having apiston rod means and a movable section having an ampule holding part.The body section and the movable section have driving means that allowsthe body section and the movable section to move relative to each otherbetween an ampule insertion position at which the ampule is insertedinto the ampule holding part of the movable section and a settingposition at which the movable section is closest to the body section.

In the above-described construction, when the body section and themovable section are placed at the ampule insertion position, the ampuleis inserted into the ampule insertion space. At this time, the insertedampule can be held removably temporarily. When the body section and themovable section are placed at the setting position by the driving means,the ampule can be fixedly held.

With the above-described construction, it is unnecessary to disassemblethe injection apparatus. Thus, the ampule can be mounted on theinjection apparatus easily.

Preferably, the driving means comprises screw feeding means. The screwfeeding means has a guide screw shaft located on the body section and anut-type operation knob mounted on the movable section such that theoperation knob is unmovable in the axial direction thereof, rotatable,and screws on a periphery of the guide screw shaft.

With the above-described construction, the nut-type operation knobscrews on the periphery of the guide screw shaft. Thus, when thenut-type operation knob is rotated, the nut-type operation knob movesalong the guide screw shaft together with the movable section. That is,with the above-described construction, the movable section and the bodysection can be moved relative to each other. This construction isparticularly advantageous when the ampule contains two components ofmedicine (agent) and it is necessary to press the piston carefully inorder to mix them with each other slowly. In such a case, the nut-shapedoperation knob and the screw part of the guide screw shaft may beappropriately selected and constructed to allow the movable section andthe body section to move slowly relative to each other when rotating thenut-shaped operation knob without taking particular care.

Preferably, the ampule has a flange, and the ampule-gripping meanscomprises a flange hold-down part and a flange pressing part The flangehold-down part is formed at a predetermined position of the ampuleinsertion space of the movable section, contacts a front surface of theflange of the inserted ampule, and moves the ampule rearward by pressingthe front surface of the flange of the ampule when the movable sectionmoves to the setting position. The flange pressing part is provided onthe body section around the piston rod means and is pressed against arear surface of the flange of the ampule when the movable section andthe body section are placed at the setting position.

With the above-described construction, when the ampule is inserted intothe ampule insertion space and when the movable section and the bodysection are positioned at the setting position, the flange of the ampuleis sandwiched between the flange hold-down part and the flange pressingpart with the front surface of the flange in contact with the flangehold-down part and the rear surface thereof in contact with the flangepressing part. That is, the movement of the ampule is fixed in its axialdirection.

Preferably, the flange pressing part comprises a spacer and an elasticO-ring. The spacer freely engages the periphery of the piston rod meansand is placed at a predetermined position of the ampule insertion spacewhen the movable section is located at the ampule insertion position sothat the spacer substantially contacts the rear surface of the flange ofthe ampule. The elastic O-ring is provided at a predetermined positionof the periphery of the piston rod means such that the elastic O-ring isaxially unmovable and pressed against a rear surface of the spacer whenthe movable section is located at the setting position.

In the above-described construction, the flange of the ampule pressesthe spacer rearward along the guide sleeve. When the movable sectionreaches the setting position, one surface of the spacer contacts therear surface of the flange of the ampule with the outer surface of thespacer being pressed by the elastic O-ring. Accordingly, the flange ofthe ampule is fixed axially through the spacer by the elastic force ofthe elastic O-ring without a backlash.

Preferably, the piston rod means comprises a guide sleeve, a piston rod,and a screw rod. The guide sleeve is fixed to the body section, projectsforward from the body section, is concentric with the inserted ampule,and has an outer diameter generally equal to an inner diameter of thesyringe of the ampule. The piston rod is inserted into the guide sleevesuch that the piston rod is nonrotatable with respect to the guidesleeve and axially slidable, and the piston rod has a screw hole. Thescrew rod has a screw part, formed at a front end thereof, and screwingon a screw part of the screw hole of the piston rod, and has anoperation knob formed at a rear end thereof. The screw rod is movabletogether with the piston rod between an initial position and apushing-in position.

In the above-described construction, the front end of the screw rodscrews on the piston rod and the piston rod does not rotate. Therefore,when the operation knob positioned at the rear end of the screw rod isrotated to rotate the screw rod, the piston rod moves relative to thescrew rod. Thus, when the piston rod is moved forward relative to thescrew rod at the initial position, and when the screw rod is pushed inup to the pushing-in position, the piston of the ampule is displacedcorrespondingly. That is, an injection amount can be set whichcorresponds to the rotation amount of the screw rod. The injectionamount can be set at the initial position, and can be set again when thescrew rod is returned from the pushing-in position to the initialposition.

In the above-described construction, the piston rod moves forward orbackward relative to the screw rod, depending upon the rotationaldirection of the screw rod. In order to set a subsequent injectionamount after an injection is given to a patient, it is necessary to feedthe piston rod forward relative to the screw rod by rotating the screwrod after the screw rod is returned to the initial position. If thescrew rod is rotated reversely to move the piston rod rearward relativeto the screw rod, there is a gap formed between the piston rod and thepiston of the ampule when the screw rod is pushed in next. As a result,it is not possible to give the injection even though the screw rod ispressed.

Accordingly, preferably, the piston rod means further comprises rotationregulation means for regulating the rotational direction of the screwrod in one direction.

With the above-described construction, the rotational direction of thescrew rod is limited to the direction in which the piston rod is movedforward relative to the screw rod. Thus, an erroneous operation insetting the injection amount can be prevented.

Preferably, the injection apparatus further comprises detection means,display means, and rotation regulation release means. The detectionmeans detects the rotational amount of the screw rod of the piston rodmeans and detects a return of the screw rod from the pushing-in positionto the initial position. The display means displays an injection amountwhich corresponds to the rotational amount of the screw rod of thepiston rod means after the screw rod returns to the initial position.The rotation regulation release means releases the rotation regulationmeans of the piston rod means when the ampule is to be removed from theampule insertion space.

In the above-described construction, based on signals, outputted fromthe detection means, which indicate the rotational amount of the screwrod and the return thereof to the initial position, the display meansdisplays an injection amount which corresponds to the amount of therotation of the screw rod after the return of the screw rod to theinitial position. Thus, it is always possible to check the injectionamount set.

Further, the rotation regulation release means releases the rotationregulation means of the piston rod means, which allows the piston rod tobe moved rearward by rotating the screw rod reversely. Therefore, aninconvenience that the ampule cannot be removed from the ampuleinsertion space because the piston rod is present in the syringe of theampule is eliminated.

In the above-described construction, when the screw rod is rotatedrelative to the piston rod in setting an injection amount, there are twocases, one in which the piston rod moves forward and the other in whichthe piston rod moves rearward axially relative to the body section ofthe injection apparatus. When the piston rod moves forward axially, aninjection amount can be set by moving the piston rod until the pistonrod contacts the piston of the syringe. But if the piston rod is movedfurther than that, the piston rod presses the piston of the syringe,thus pressing out medicine therefrom. Thus, there is a restriction inthe injection amount which can be set. On the other hand, when the screwrod moves rearward axially, there is no such restriction in theinjection amount which can be set. The construction in which the screwrod moves rearward axially is described below.

That is, a concave part is formed on a peripheral surface of the pistonrod. The concave part comprises a bottom surface generally parallel withan inner peripheral surface of the guide sleeve, a front step surfacebeing provided on a front side of the bottom surface and extending fromthe bottom surface outwardly in a radial direction of the piston rod,and a rear step surface being provided on a rear side of the bottomsurface and extending from the bottom surface outwardly in the radialdirection of the piston rod. The concave part may be plural. Forexample, the concave may be dovetail groove-shaped. That is, the concavemay be a long and narrow groove extending axially. The piston rod meansfurther comprises a spring means and a stopper member. The spring meansautomatically returns the screw rod and the piston rod to the initialposition when a force for pushing the screw rod and the piston rod in isreleased. The stopper member is positioned in the concave of the pistonrod, slidably contacts the bottom surface of the piston rod and theinner peripheral surface of the guide sleeve with a predeterminedfrictional force, moves together with the piston rod with the stoppermember in contact with the rear step surface of the piston rod when thepiston rod is pushed in, and stops the movement of the piston rod withthe stopper member in contact with the front step surface of the pistonrod when the piston rod is returned by the spring means. The frictionalforce between the stopper member and the bottom surface of the pistonrod is smaller than the automatic return force of the spring means. Thefrictional force between the stopper member and the inner peripheralsurface of the guide sleeve is greater than the automatic return forceof the spring means.

In the above-described construction, the frictional force between thestopper member and the bottom surface of the piston rod is smaller thanthe automatic return force of the spring means. The frictional forcebetween the stopper member and the inner peripheral surface of the guidesleeve is greater than the automatic return force of the spring means.Therefore, when the screw rod is pressed with a force greater than thefrictional force between the stopper member and the inner peripheralsurface of the guide sleeve, the stopper member positioned between thepiston rod and the guide sleeve is stationary relative to the guidesleeve, and the piston rod moves forward slidably contacting the bottomsurface of the guide sleeve. This is because the frictional forcebetween the stopper member and the bottom surface of the piston rod issmaller than the frictional force between the stopper member and theinner peripheral surface of the guide sleeve. When the stopper member isbrought into contact with the rear step surface of the piston rod, thestopper member moves, with the stopper member being pressed by the rearstep surface of the piston rod. That is, the stopper member slides incontact with the inner peripheral surface of the guide sleeve. When thepiston rod is returned by the spring means, the piston rod moves in thereturn direction until it contacts the front surface of the stoppermember because the frictional force between the stopper member and thebottom surface of the piston rod is smaller than the automatic returnforce of the spring means. That is, the bottom surface of the piston rodand the stopper member slide in contact with each other. When the pistonrod contacts the front surface of the stopper member, the stopper memberkeeps stationary relative to the guide sleeve because the frictionalforce between the stopper member and the inner peripheral surface of theguide sleeve is greater than the automatic return force of the springmeans. Accordingly, the piston rod does not move further and theposition of the piston rod becomes the initial position of a subsequentinjection. At the initial position, the screw rod is rotated to feed itrelative to the piston rod, and then the screw rod is pressed; as aresult, the piston of the syringe is pushed out. That is, it is possibleto inject an amount of medicine in correspondence to the feeding amountof the screw rod.

Accordingly, in the above-described construction, when the screw rod isrotated relative to the piston rod in setting the injection amount, thescrew rod moves rearward axially relative to the body section of theinjection apparatus.

Preferably, the stopper member is made of a frictional/elastic materialsuch as a rubber. That is, it is made of a material which is superior infrictional property. The front step surface of the piston rod is aninclined surface which extends from the bottom surface outwardly in theradial direction and towards a front side of the piston rod, and awedge-shaped space is formed between the inclined surface and the innerperipheral surface of the guide sleeve.

In the above-described construction, when the piston rod is returnedfrom the pushing-in position to the initial position by the springmeans, and the stopper member reaches the wedge-shaped space between theinclined surface of the groove and the inner peripheral surface of theguide sleeve, the stopper member fits in the wedge-shaped space as thestopper member is elastically deformed. As a result, there is anincrease in the frictional force between the stopper member and theinner peripheral surface of the guide sleeve and between the stoppermember and the inclined surface of the piston rod.

Accordingly, with the above-described construction, the piston rod isreliably fixed to the guide sleeve at the initial position.

In the above-described construction, if the pushing-in amount of thescrew rod is smaller than the stroke of the stopper member which movesbetween the front step surface of the piston rod and the rear stepsurface thereof, the stopper member is not pressed by the rear stepsurface of the piston rod when the screw rod is pushed in. As a result,the stopper member remains stationary relative to the inner peripheralsurface of the guide sleeve. Thus, when the pressed piston rod is pulledbackward by the spring means, the screw rod returns to the same positionas before it was pushed in. Therefore, the position of the screw rodmakes it impossible to determine whether an injection has been given toa patient or not. It is preferable to provide the following constructionin order to eliminate such inconvenience.

That is, preferably, the stroke of the stopper member moving between thefront step surface of the piston rod and the rear step surface thereofis smaller than the amount of the screw rod which is fed relative to thepiston rod by rotating the screw rod to set a dosage amount forinjection.

In the above-described construction, when the piston rod is pressed, thestopper member is reliably brought into contact with the rear stepsurface of the piston rod so that the stopper member is pushed in andmoved. The movement amount thereof is greater than the stroke of thestopper member which moves between the front step surface of the pistonrod and the rear step surface thereof. Thus, when the piston rod ismoved backward by the spring means, the stopper member never fails tocontact the front step surface of the piston rod. That is, after aninjection is carried out, the piston rod is returned from the pushing-inposition to the initial position in correspondence to the stroke of thestopper member which moves between the front step surface of the pistonrod and the rear step surface thereof. Thus, the position of the rearend of the screw rod relative to the injection apparatus is unchanged.

Therefore, the screw rod is not returned to the position at which it isfed rearward in order to set an injection amount, but the screw rod isreturned to a predetermined position relative to the body section of theinjection apparatus. Thus, it is easy to determine whether injection ofthe set injection amount has been given to the patient or not.

Preferably, the concave is formed as a circumferential concave, and thestopper member is a ring-shaped one provided on the circumferentialconcave.

According to the above-described construction, the number of parts to beused is small and the configuration is simple; thus, it is the mostpreferable.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view partly in section showing a conventionalinjection apparatus;

FIGS. 2A-2D are front views showing an injection apparatus according toa first embodiment of the present invention, FIGS. 2A through 2Dcorrespond to states I through IV, respectively;

FIGS. 3A-3D are front views showing the injection apparatus according tothe first embodiment of the present invention, FIGS. 3A through 3Dcorrespond to states V through VIII, respectively;

FIG. 4 is an enlarged sectional view showing the injection apparatus inthe state I shown in FIG. 2A;

FIG. 5 is an enlarged sectional view showing the injection apparatus inthe state II shown in FIG. 2B;

FIG. 6 is an enlarged sectional view showing the injection apparatus inthe state III shown in FIG. 2C;

FIG. 7 is an enlarged sectional view showing the injection apparatus inthe state IV shown in FIG. 2D;

FIG. 8 is an enlarged sectional view showing the injection apparatus inthe state V shown in FIG. 3A;

FIG. 9 is an enlarged sectional view showing the injection apparatus inthe state VI shown in FIG. 3B;

FIG. 10 is an enlarged sectional view showing the injection apparatus inthe state VIII shown in FIG. 3D;

FIG. 11 is a sectional view taken along a line XI--XI of FIG. 4;

FIG. 12 is a sectional view taken along a line XII--XII of FIG. 4;

FIG. 13 is a sectional view taken along a line XIII--XIII of FIG. 6;

FIG. 14 is a sectional view taken along a line XIV--XIV of FIG. 7;

FIG. 15 is an enlarged sectional view showing an injection apparatusaccording to a second embodiment of the present invention, and the stateof the injection apparatus corresponds to the state II shown in FIG. 2B;

FIG. 16 is an enlarged sectional view showing the injection apparatusaccording to the second embodiment of the present invention, and thestate of the injection apparatus corresponds to the state II shown inFIG. 2B;

FIG. 17 is a sectional view showing the injection apparatus of FIGS. 15and 16, and the state of the injection apparatus corresponds to thestate II shown in FIG. 2B;

FIG. 18 is a sectional view showing the injection apparatus of FIGS. 15and 16, and the state of the injection apparatus corresponds to thestate III shown in FIG. 2C;

FIG. 19 is a sectional view showing the injection apparatus of FIGS. 15and 16, and the state of the injection apparatus corresponds to thestate IV shown in FIG. 2D;

FIG. 20 is a sectional view showing the injection apparatus of FIGS. 15and 16, and the state of the injection apparatus corresponds to thestate V shown in FIG. 3A; and

FIG. 21 is a sectional view showing the injection apparatus of FIGS. 15and 16, and the state of the injection apparatus corresponds to thestate VI shown in FIG. 3B.

BEST MODE FOR CARRYING OUT THE INVENTION

An injection apparatus according to each embodiment of the presentinvention shown in FIGS. 2 through 21 is described below in detail.

A first embodiment is described below with reference to FIGS. 2 through14.

As shown in FIG. 2A, an injection apparatus 10 comprises a body section20 and a movable section 30. The body section 20 has a release button 40and an operation knob 50 at the rear end thereof and an indicator 61 atone side thereof. The body section 20 fits in the rear casing 31 of themovable section 30. A front casing 32 of the movable section 30 has anoperation knob 34 positioned at an upper cut-out 33 thereof and anampule holding part 36 at a lower portion thereof.

An ampule 70 particularly preferable for the injection apparatus 10 is atwo-component ampule as shown by chain lines in FIG. 2A and has a flange75 at an end thereof opposite to an end thereof on which aneedle-mounting part 76 is mounted. The ampule 70 has two pistons 72 and74 inside a syringe 77 thereof. One component of the two-component agent(base) is contained in a first chamber 71 and the other componentthereof is contained in a second chamber 73 partitioned from the firstchamber 71. For example, a dry powder agent (base) prepared by freezedrying is contained in the first chamber 71, while disolving agent(base) separate from the powder agent (base) is contained in the secondchamber 73. Both components are mixed with each other at time ofinjection.

As shown by an arrow in FIG. 2A, the ampule 70 is inserted into theampule holding part 36 from below the front casing 32 of the movablesection 30, and the operation knob 34 is rotated to move the movablesection 30 rearward together with the ampule 70. Then, a needle unit 80is mounted on the needle-mounting part 76 of the ampule 70 to set theampule 70 on the injection apparatus 10, as shown in FIG. 2D. After theampule 70 is set on the injection apparatus 10, the operation knob 50 isrotated to set an injection amount, and then, pressed axially to carryout an injection.

The construction of the injection apparatus 10 will be described furtherin detail with reference to FIGS. 2A, 4, and 11.

FIG. 4 is a sectional view corresponding to an initial state shown inFIG. 2A. In the injection apparatus 10, a cylindrical guiding wall 28constituting the casing of the body section 20 slidably fits in the rearcasing 31 of the movable section 30. In the body section 20, a guidesleeve 22 projects forward concentrically with the axis of the ampule 70(hereinafter referred to as merely "axis") when the ampule 70 is set onthe injection apparatus 10, and a guide screw shaft 26 projects forwardin parallel with the axis.

The guide sleeve 22 has a peripheral surface 22a, the outer diameter ofwhich is generally equal to an inner diameter of the syringe 77 of theampule 70. As shown in FIG. 11, showing the injection apparatus in adirection perpendicular to the axis, a peripheral cut-out 22b is formedon a part of the peripheral surface 22a. An O-ring 24 is provided on abase part 22d of the guide sleeve 22. A spacer 25 which freely engagesthe peripheral surface 22a of the guide sleeve 22 is provided ahead ofthe O-ring 24. The outer diameter of the spacer 25 is generally equal tothat of the flange 75 of the ampule 70.

A through-hole 23 is formed in the guide sleeve 22. A piston rod 54engages the through-hole 23 nonrotatably and movably in its axialdirection. That is, as shown in FIG. 11, the through-hole 23 of theguide sleeve 22 is generally circular in section, and projections 23aproject inward from the guide sleeve in four directions, each adjacentone of which forms a 90° angle. On the other hand, the sectionalconfiguration of the piston rod 54 corresponds to that of thethrough-hole 23. Thus, the piston rod 54 is movable axially through thethrough-hole 23 without rotating therein. In an initial state, thepiston rod 54 is retracted inside the through-hole 23 of the guidesleeve 22, and a front end 22c of the guide sleeve 22 and that of thepiston rod 54 are generally in the same plane.

The piston rod 54 has a hole in its center, and a female screw 54a isformed on the hole. A screw rod 52 having a male screw 52a, whichengages the female screw 54a, formed on a front part thereof and havingthe operation knob 50 fixed to the rear end thereof is connected withthe piston rod 54 by means of the screws.

The screw rod 52 penetrates through a through-hole 56a of a ratchet 56and a through-hole 55c of an encoder cam 55. The ratchet 56 positionedforward and the encoder cam 55 positioned rearward are fixed to eachother and they rotate without moving axially.

The screw rod 52 has a spline shaft portion 52b projecting outward at anintermediate part thereof. A spline part 56b is formed at a front sideof the through-hole 56a of the ratchet 56. The spline shaft portion 52bof the screw rod 52 engages the spline part 56b of the ratchet 56. Thusthe screw rod 52, the ratchet 56, and the encoder cam 55 always rotatetogether.

The screw rod 52 has a return spring 57 between the encoder cam 55 andthe operation knob 50. The return force of the return spring 57 alwaysurges the screw rod 52 backward.

A flange 56c is formed at a front end of the ratchet 56. The returnforce of the return spring 57 causes the flange 56c to be always incontact with a ratchet contact part 21 of the body section 20.

The ratchet 56 has a ratchet part 56d, facing forward, formed in back ofthe flange 56c. A rotation regulation plate 58 positioned between theratchet part 56d and the flange 56c, and having a through-hole throughwhich the ratchet 56 penetrates, is mounted axially movable to the bodysection 20. A ratchet 58a facing the ratchet part 56d of the ratchet 56is formed on a rear side of the rotation regulation plate 58. A returnspring 59 is provided between the front side of the rotation regulationplate 58 and the ratchet contact part 21 of the body section 20. Thereturn force of the return spring 59 urges the rotation regulation plate58 backward, thus always allowing engagement between the ratchet 58a ofthe rotation regulation plate 58 and the ratchet portion 56d of theratchet 56.

A guide screw shaft 26 of the body section 20 will be described below.The guide screw shaft 26 projects forward in parallel with the axis. Amale screw 26a is formed on the periphery of the guide screw shaft 26,and a through-hole 27 is formed in the center thereof.

The male screw 26a engages a female screw 34a formed in a center hole ofthe operation knob 34 of the movable section 30.

A rotation regulation release pin 46 penetrates through the through-hole27. A spring accommodating part 27a is formed at the front side of thethrough-hole 27. A spring flange 46b is fixed to a front end of therotation regulation release pin 46. A return spring 46a is providedbetween the spring flange 46b and the spring accommodating part 27a. Thereturn force of the return spring 46a urges the rotation regulationrelease pin 46 forward.

On the other hand, the rear end of the rotation regulation release pin46 penetrates through the rotation regulation plate 58, and a releaseflange 46c is fixed to the rotation regulation release pin 46 behind therotation regulation plate 58. When the rotation regulation release pin46 is moved forward, the rotation regulation plate 58 is moved forwardby the release flange 46c.

The movable section 30 will be described below. As shown in FIGS. 2A, 4,and 11, the ampule holding portion 36 is formed at a lower part of thefront casing 32 of the movable section 30. That is, the ampule holdingpart 36 comprises a pair of ampule securing elastic wings 36a formed onboth sides of a lower part of the front casing 32. As shown in FIG. 11,the pair of ampule securing elastic wings 36a is generally C-shaped inits sectional view taken perpendicular to the axis. The inner peripheralsurface of the pair of ampule securing elastic wings 36a forms an ampuleinsertion space 36f into which the ampule 70 is inserted. The diameterof the inner peripheral surface of the pair of ampule securing elasticwings 36a is generally equal to the outer diameter of the syringe 77 ofthe ampule 70. A side edge 36b at a lower inner side of each ampulesecuring elastic wing 36a forms a lower opening 36c. Further, the frontend 36d of the pair of ampule securing elastic wings 36a forms a frontopening 36e. The distance between both side edges 36b of the pair ofampule securing elastic wings 36a is shorter than the outer diameter ofthe syringe 77 of the ampule 70 by a predetermined amount.

A center of the lower part of the front casing 32 is cut out to form aflange insertion part 38 into which the flange 75 of the ampule 70 isinserted. The spacer 25 is positioned at the flange insertion part 38,and the rear side of the spacer 25 fits in the front casing 32 of themovable section 30.

The operation knob 34 which is unmovable axially and rotatable isprovided on the upper cut-out 33 of the front casing 32. A through-hole34a is formed in the center of the operation knob 34, and a screw 34b isformed on the inner peripheral surface of the operation knob 34. Thefemale screw 34b engages the male screw 26a formed on the periphery ofthe guide screw shaft 26 of the body section 20. The operation knob 34has a bearing part 34c formed at each end thereof and is supported by abearing part 33a of the front casing 32.

The rear casing 31 of the movable section 30 is cut out at apredetermined position thereof to form a display window 39 to which atransparent plate is fixed. An indicator 61 of the body section 20 isseen through the display window 39 when the ampule 70 is set in theinjection apparatus 10.

Description of the method of operating the injection apparatus 10 andthe detailed construction thereof, will be made below.

In the initial state shown in FIGS. 2A and 4, the ampule 70 is insertedfrom below into the ampule holding part 36 of the movable section 30placed at the ampule insertion position.

At this time, the movable section 30 is forwarded from the body section20 to its maximum, and the piston rod 54 is retracted inside the guidesleeve 22 of the body section 20, as described above. Because the guidesleeve 22 and the piston rod 54 are not projected into the ampuleinsertion space 36f at this time, the ampule 70 can be inserted into theampule holding part 36 without interference. On the other hand, in anincomplete initial state, the guide sleeve 22 and/or the piston rod 54project into the ampule insertion space 36f, so that the ampule 70cannot be inserted into the ampule holding part 36. This is because theyinterfere with the ampule 70. That is, unless the injection apparatus 10is in the complete initial state, the ampule 70 cannot be inserted intothe ampule holding part 36.

In the initial state, the rotation regulation release pin 46 moves therotation regulation plate 58 forward by means of the urging force of thereturn spring 46a against the urging force of the return spring 59 whichurges the rotation regulation plate 58 backward. As a result, theratchet 58a of the rotation regulation plate 58 and the ratchet part 56dof the ratchet 56 disengages from each other. Accordingly, the screw rod52 can be rotated in both directions, and hence it is possible to movethe piston rod 54 back.

As shown in FIG. 11, in the ampule-inserting operation, the ampule 70 ispressed in the lower opening 36c of the pair of ampule securing elasticwings 36a. Then, the ampule securing elastic wings 36a are expandedoutward, allowing insertion of the ampule 70 into the ampule insertionspace 36f. After the ampule 70 is inserted thereinto, the ampulesecuring elastic wings 36a are returned to their original form, thuspreventing the ampule 70 from moving in a direction perpendicular to theaxis of the ampule 70. At the same time, the flange 75 of the ampule 70is inserted into the flange insertion part 38, thus preventing theampule 70 from moving in the axial direction as well. Accordingly, theampule 70 is held temporarily in the axial direction and the directionperpendicular thereto.

Then, as shown in FIGS. 2B and 5, the operation knob 34 is rotated in apredetermined direction to move the movable section 30 to a settingposition at which the movement of the ampule 70 is completed.

That is, the female screw 34b of the operation knob 34 of the movablesection 30 engages the male screw 26a of the guide screw shaft 26 of thebody section 20. Thus, due to the rotation of the operation knob 34, theoperation knob 34 moves along the guide screw shaft 26. As a result, theentire movable section 30 moves relative to the body section 20. Thus,the entire movable section 30 is moved toward the body section 20 byrotating the operation knob 34 in a predetermined direction.

Because the flange 75 of the ampule 70 has fitted in the flangeinsertion part 38 of the movable section 30, the ampule 70, held by theampule holding part 36 of the movable section 30, moves toward the bodysection 20 together with the movable section 30. At this time, the guidesleeve 22 of the body section 20 is inserted into the syringe 77 of theampule 70. The guide sleeve 22 can be inserted into the syringe 77smoothly, with the peripheral surface 22a of the guide sleeve 22 insliding contact with the inner peripheral surface of the syringe 77 ofthe ampule 70, because the peripheral cut-out 22b formed on the guidesleeve 22 reduces the frictional force between the peripheral surface22a and the inner peripheral surface of the syringe 77.

The front end 22c of the guide sleeve 22 contacts the rear end surfaceof the second piston 74 of the ampule 70, thus pushing in the secondpiston 74. At the same time, the first piston 72 moves, with themedicine contained in the second chamber 73, allowing a predeterminedinterval to be kept between the first piston 72 and the second piston74. When the first piston 72 reaches a bypass part 78 at which a portionof the inner peripheral surface of the syringe 77 projects outward, thefirst chamber 71 and the second chamber 73 communicate with each otherthrough the bypass part 78. As a result, the medicine in the secondchamber 73 moves from the rear side of the first piston 72 to the firstchamber 71 through the bypass part 78, with the medicine in the secondchamber 73 being pressed by the second piston 74. At this time, thefirst piston 72 does not move, but the second piston 74 moves until itcontacts the first piston 72. In this manner, the medicine in the firstchamber 71 and that in the second chamber 73 are mixed with each other.Depending on the kind of medicine, such mixture should be carried outvery carefully and slowly. In such a case, the operation knob 34, thefemale screw 34b of the operation knob 34, and the male screw 26a of theguide screw shaft 26 may be appropriately selected in construction sothat the medicines are mixed together slowly even if it is operatednormally without taking much care.

When the guide sleeve 22 is inserted into the syringe 77 of the ampule70, the ampule 70 is incapable of moving in a direction perpendicular tothe axial direction thereof.

As the movable section 30 moves, a rear end surface 75b of the flange 75of the ampule 70 pushes the spacer 25 installed around the guide sleeve22. At the set position at which the movement of the movable section 30is completed, the spacer 25 presses the O-ring 24 positioned at the baseportion 22d of the guide sleeve 22. The flange 75 of the ampule 70 isurged forward through the spacer 25 by the elastic force of the O-ring24, while a front end surface 75a of the flange 75 contacts a front endsurface 38a of the flange insertion part 38 of the movable section 30.Accordingly, the ampule 70 is held free from backlash in the axialdirection thereof.

Then, the needle unit 80 is installed on the needle-mounting part 76 ofthe ampule 70, and then air inside the syringe 77 of the ampule 70 isreleased.

As shown in FIGS. 2C and 6, in order to release the air completely fromthe syringe 77, the piston rod 54 is moved forward to press the pistons72 and 74 forward by pressing the operation knob 50 forward. At thistime, the screw rod 52 moves together with the piston rod 54 from aninitial position to a pressing position. That is, the spline shaft part52b of the screw rod 52 moves axially forward from the initial positionwhile the spline shaft part 52b keeps engaging the spline part 56b ofthe ratchet 56. Then, a stopper strip 42a of a stopper plate 42 fits ina stopper groove 50c of the operation knob 50, thus providing thepressing position.

Then, the release button 40 is pressed to return the screw rod 52 andthe piston rod 54 to the initial position, as shown in FIGS. 2D and 7.At this time, as shown by a dotted line of FIG. 13, a stopper releasepart 40c of the release button 40 moves a reset strip 42b of the stopperplate 42 to the left side in FIG. 13, thus rotating the stopper plate 42on a stopper-supporting pin 44. As a result, the stopper strip 42a isunlocked from the stopper groove 50c of the operation knob 50. Then, thescrew rod 52 and the piston rod 54 are returned to the initial positionby the return force of the return spring 57. The return thereof to theinitial position is detected by a stopper position detector (not shown).

In this state, the setting of the ampule 70 is completed. The indicator61 displays an initial value 0.0 upon receipt of signals outputted fromthe stopper position detector.

Then, in order to set an injection amount, the operation knob 50 isrotated in a predetermined direction, as shown in FIGS. 3A and 8. By theoperation, the piston rod 54 is moved forward relative to the screw rod52. The amount of the forward movement of the piston rod 54 correspondsto the injection amount. When the screw rod 52 is rotated in thepredetermined direction, the contact inclined surface of the ratchetpart 56d of the ratchet 56 presses the ratchet 58a of the rotationregulation plate 58 forward against the return force of the returnspring 59. Thus, the screw rod 52 is rotatable. When the screw rod 52 isrotated in the opposite direction, the surface of the ratchet part 56din the axial direction and that of the ratchet 58a in the axialdirection engage each other, thus preventing rotation of the screw rod52. Accordingly, the operation knob 50 is rotatable only in thedirection in which the injection amount can be set by moving the pistonrod 54 forward.

As shown in FIG. 14 which is a sectional view of the injection apparatus10, the amount of rotation of the screw rod 52 made by rotating theoperation knob 50 is detected by a detection switch 62, the contactpoint of which is opened and closed depending on the position of theencoder cam 55. Upon receipt of signals outputted from the detectionswitch 62, the indicator 61 displays an injection amount correspondingto the signals.

As shown in FIGS. 3B and 9, after the injection amount is set, injectionis carried out by pressing the operation knob 50 forward after a patientis pricked with the needle. Because the piston rod 54 has moved forwardin correspondence to the amount of the rotation of the operation knob 50made immediately before the operation knob 50 is pressed forward, thepistons 72 and 74 are pushed forward in correspondence to the amount ofthe forward movement of the piston rod 54.

After one dosage of injection is completed, the needle unit 80 isremoved from the ampule 70 as shown in FIG. 3C and it can be stored.

When injections are repeatedly performed, the release button 40 ispushed forward to return the screw rod 52 and the piston rod 54 to theinitial position, as described above. At this time, the indicator 61displays the initial value 0.0 upon receipt of signals outputted fromthe stopper position detector (not shown).

When the ampule 70 is removed from the injection apparatus 10, the screwrod 52 is returned to the initial position, and the operation knob 50 isrotated reversely. Because the ratchet 56 and the rotation regulationplate 58 prevent the reverse rotation of the operation knob 50, therelease button 40 is pressed deep to rotate the operation knob 50reversely, as shown in FIGS. 3D and 10. That is, a rear end of thestopper-supporting pin 44 is pressed forward by the bottom surface of aspring-accommodating part 40b of the release button 40. As a result, arelease flange 44a of the stopper-supporting pin 44 presses the rotationregulation plate 58 forward, thus disengaging the ratchet part 56d ofthe ratchet 56 and the ratchet 58a of the rotation regulation plate 58from each other. Accordingly, the screw rod 52 can be rotated reversely.

By rotating the operation knob 50 reversely, the piston rod 54 isreturned into the guide sleeve 22 completely so as to return the movablesection 30 to the ampule insertion position in a procedure opposite tothat described above. At this time, because the ampule 70 is temporarilyheld by the ampule securing elastic blades 36a and the flange insertionportion 38 in the axial direction and the direction perpendicularthereto, the ampule 70 can be prevented from falling out of theinjection apparatus 10. The ampule 70 is pulled downward from theinjection apparatus 10 in a direction perpendicular to the axialdirection against the elastic force of the securing elastic blades 36a.

With the above-described construction of the injection apparatus 10, theampule 70 can be easily installed thereon; in addition, the state of theinjection liquid inside the ampule 70 can be easily seen.

The present invention is not limited to the above-described embodiment,but may be embodied in various other modes. For example, the drivingmeans for moving the movable section relative to the body section may beconstituted by a rack and a pinion.

In respect of the piston rod means of the first embodiment, when theoperation knob 50 is rotated to set an injection amount, the piston rod54 is fed forward and the screw rod 52 is stationary with respect to thebody section 20. On the other hand, it is possible to feed the screw rodrearward by rotating the operation knob, with the piston rod beingstationary.

An injection apparatus according to a second embodiment of the presentinvention will be described below in detail with reference to FIGS. 15through 21. FIGS. 15 and 16 are enlarged sectional views showing aninjection apparatus when an ampule is installed in the injectionapparatus. FIGS. 17 through 21 are sectional views showing the injectionapparatus at each operational step.

The injection apparatus of the second embodiment is constructedsimilarly to the first embodiment except the piston rod means.Description will be made below mainly on the points of the secondembodiment which are different from the first embodiment. It is to benoted that in FIGS. 15 through 21, component parts of the secondembodiment having the same constructions as those of the firstembodiment are denoted by the same reference numerals, respectively,whereas component parts of the second embodiment having differentconstructions from those of the first embodiment are denoted byattaching a suffix "s" to reference numerals of the first embodiment todistinguish them from each other.

The construction of the piston rod means of an injection apparatus 10sof the second embodiment is substantially the same as that of the pistonrod of the first embodiment. That is, as shown in FIGS. 15 and 16,similarly to the first embodiment, a piston rod 54s has a hole in itscenter, and a female screw 54a is formed on the hole and connected witha male screw 52a formed at a front end of the screw rod 52.

Unlike the first embodiment, the peripheral surface of the piston rod54s is constructed stepwise. That is, a groove is circumferentiallyformed at a center of the peripheral surface of the piston rod 54s. Theouter diameter of a front sliding part 54ps defining the peripheralsurface of the front side of the piston rod 54s is smaller than that ofa rear sliding part 54qs defining the peripheral surface of the rearside thereof. A stopper sliding part 54ys is formed at the rear side ofthe bottom surface of the groove, whereas a tapered part 54xs is formedat the front side of the bottom surface of the groove. The outerdiameter of the stopper sliding part 54ys is smaller than that of thefront sliding portion 54ps, and the tapered part 54xs is continuously,smoothly formed between the front sliding part 54ps and the stoppersliding part 54ys. A step 54ws is formed at the boundary between thestopper sliding part 54ys and the rear sliding part 54qs.

Unlike the first embodiment, the inner peripheral surface of a guidesleeve 22s is different from that of the first embodiment. That is, afront inner peripheral surface 22ps and a rear inner peripheral surface22qs are formed stepwise. The inner diameter of the front innerperipheral surface 22ps is smaller than that of the rear innerperipheral surface 22qs, and a step 22ws is formed at the boundarybetween both inner peripheral surfaces 22ps and 22qs. The front innerperipheral surface 22ps of the guide sleeve 22s slides in contact withthe front sliding portion 54ps of the piston rod 54s, and the rear innerperipheral surface 22qs of the guide sleeve 22s slides in contact withthe rear sliding part 54qs of the piston rod 54s.

The inner peripheral surface of a stopper ring 54ms serving as a stoppermember, not used in the first embodiment, slidably engages the stoppersliding part 54ys of the piston rod 54s and the tapered part 54xsthereof. The peripheral surface of the stopper ring 54ms slides incontact with the rear inner peripheral surface 22qs of the guide sleeve22s and is axially movable between the step 22ws of the guide sleeve 22sand the step 54ws of the piston rod 54s.

The frictional force of the stopper ring 54ms, which slides in contactwith both the guide sleeve 22s and the piston rod 54s, satisfies thefollowing condition.

That is, the frictional force Fo between the peripheral surface of thestopper ring 54ms and the rear inner peripheral surface 22qs of theguide sleeve 22s is greater than the frictional force Fi between theinner peripheral surface of the stopper ring 54ms and the stoppersliding part 54ys of the piston rod 54s and between the inner peripheralsurface of the stopper ring 54ms and the tapered part 54xs thereof. Thatis,

    Fi<Fo                                                      (1)

The return force (P) of the return spring 57 for urging the screw rod 52rearward axially is greater than the frictional force Fi between theinner peripheral surface of the stopper ring 54ms and the stoppersliding part 54ys of the piston rod 54s and between the inner peripheralsurface of the stopper ring 54ms and the tapered part 54xs thereof, andthe return force (p) is smaller than the frictional force Fo between theperipheral surface of the stopper ring 54ms and the rear innerperipheral surface 22qs of the guide sleeve 22s. That is,

    Fi<P<Fo                                                    (2)

As will be described later, a pullback force (T) for forcibly pullingthe screw rod 52 rearward is greater than the frictional force Fobetween the peripheral surface of the stopper ring 54ms and the rearinner peripheral surface 22qs of the guide sleeve 22s. That is,

    Fo<T                                                       (3)

From the equations (1) through (3), the following equation (4) isestablished:

    Fi<P<Fo<T                                                  (4)

The method of operating the injection apparatus 10s and the constructionthereof will be described below in detail. The injection apparatus 10sis operated similarly to the first embodiment, but the operations of thepiston rod 54s and the screw rod 52 are different from those of thefirst embodiment.

Similarly to the first embodiment, the ampule 70 is inserted into theinjection apparatus 10s, the operation knob 34 is rotated to move themovable section 30 to the setting position, the needle unit 80 isinstalled on the needle-mounting portion, and then air inside thesyringe 77 of the ampule 70 is released. The state at this time is shownin FIG. 17 corresponding to the state II of FIG. 2B, and in FIGS. 15 and16 which are enlarged views of the injection apparatus 10s.

As shown in FIG. 18 corresponding to the state III of FIG. 2C, in orderto release air completely from the syringe 77, the piston rod 54s ismoved forward to press the piston rods 72 and 74 forward by pushing theoperation knob 50 forward. That is, similarly to the first embodiment,the screw rod 52 moves together with the piston rod 54s from the initialposition to the pressing position. That is, the screw rod 52 movesforward until the stopper strip 42a engages the stopper groove 50c ofthe operation knob 50, while the spline shaft part 52b of the screw rod52 moves axially in engagement with the spline part 56b of the ratchet56.

At this time, because the frictional force Fo between the stopper ring54ms and the guide sleeve 22s is greater than the frictional force Fibetween the stopper ring 54ms and the piston rod 54s as shown by theexpression (1), the stopper ring 54ms keeps stationary with respect tothe guide sleeve 22, while the piston rod 54s moves in sliding contactwith the stopper ring 54ms. When the step 54ws of the groove of thepiston rod 54s reaches the rear end surface of the stopper ring 54ms,the stopper ring 54ms is pressed by the step 54ws of the groove of thepiston rod 54s, thus moving in sliding contact with the inner peripheralsurface of the guide sleeve 22s. This is because the force of pressingthe piston rod 54s forward is greater than the frictional force Fobetween the stopper ring 54ms and the guide sleeve 22s.

Then, as shown in FIG. 19 corresponding to the state IV of FIG. 2D, therelease button 40 is pressed to return the screw rod 52 and the pistonrod 54s to the initial position. That is, similarly to the firstembodiment, the stopper strip 42a is unlocked from the stopper groove50c of the operation knob 50, and the screw rod 52 and the piston rod54s are urged toward the initial position by the return force (P) of thereturn spring 57.

At this time, based on the condition of the expression (2), the stopperring 54ms keeps stationary with respect to the guide sleeve 22s, and thepiston rod 54s moves in sliding contact with the inner peripheralsurface of the stopper ring 54ms. When the tapered part 54xs of thepiston rod 54s reaches the stopper ring 54ms, the stopper ring 54ms fitsin a wedge-shaped space located between the tapered part 54xs and therear inner peripheral surface 22qs of the guide sleeve 22s.Consequently, the piston rod 54s is prevented from moving further, andthe return of the screw rod 52 and the piston rod to the initialposition is completed.

Similarly to the first embodiment, the return of the screw rod and thepiston rod to the initial position is detected by a stopper positiondetector (not shown) for detecting the position of the stopper plate 42.The setting of the ampule 70 is completed with this state. At the sametime, the indicator 61 displays the initial value 0.0 upon receipt ofsignals outputted from the stopper position detector.

In order to set an injection amount, the operation knob 50 is rotated ina predetermined direction, as shown in FIG. 20 corresponding to thestate V shown in FIG. 3A.

At this time, the stopper ring 54ms which has fitted in the tapered part54xs prevents the piston rod 54s from moving axially. Therefore, uponrotation of the operation knob 50, the screw rod 52 is fed rearward withrespect to the piston rod 54s and thus the total length of the pistonrod 54s and the screw rod 52 becomes longer. That is, in this point, thesecond embodiment is different from the first embodiment in which thepiston rod 54 is fed forward with respect to the screw rod 52.

The second embodiment is similar to the first embodiment in otherpoints. The amount of the movement thereof corresponds to an injectionamount, and a set injection amount is displayed by the indicator 61. Theoperation knob 50 can be rotated in only a direction in which theinjection amount can be set by the ratchet mechanism.

After the injection amount is set, as shown in FIG. 21 corresponding tothe state VI shown in FIG. 3B, an injection is given to a patient bypressing the operation knob 50 forward after the patient is pricked withthe needle, similarly to the first embodiment. At this time, the screwrod 52 is pushed in up to a predetermined position at which the stopperstrip 42a engages the stopper groove 50c of the screw rod 52. Thedistance between the stopper groove 50c of the screw rod 52 and thefront end of the piston rod 54s at which the piston rod 54s contacts thepiston 74 is increased by an amount corresponding to the rotation amountof the operation knob 50. Thus, the pistons 72 and 74 are pushed forwardin correspondence to the extending amount thereof, thus giving aninjection of the set amount to the patient. The stopper ring 54ms movesin the groove of the piston rod 54s between the tapered part 54xsthereof and the step 54ws thereof. Normally, the above extending amountof the length, of the screw rod 52 and the piston rod 54s, set by theoperation knob 50 is greater than the stroke of the stopper ring 54rms,namely, the distance covered by the relative movement of the stopperstrip 42a to the piston rod 54s between the tapered part 54xs and thestep 54ws thereof. Therefore, for every injection, the stopper ring 54msis pushed by the step 54ws of the groove of the piston rod 54s, thusmoving forward along the inner peripheral surface of the guide sleeve22s.

When injections are repeated, the release button 40 is pressed to returnthe screw rod 52 and the piston rod 54s to the initial position, and theabove-described procedure is repeatedly performed. While injections arerepeated in the above-described procedure, the stopper ring 54ms movesforward only, and does not move rearward. Accordingly, as injections arerepeated, the initial position of the piston rod 54s and that of thestopper ring 54ms move forward.

When the ampule 70 is removed from the injection apparatus 10s, thescrew rod 52 is returned to the initial position, and then, theoperation knob 50 is forcibly moved rearward to move the piston rod 54sand the stopper ring 54ms rearward.

At this time, because the frictional force Fo between the stopper ring54ms and the guide sleeve 22s is smaller than the pullback force (T) bywhich the screw rod is forcibly pulled back, the stopper ring 54ms whichreaches the tapered part 54xs of the piston rod 54s moves rearwardtogether with the piston rod 54s, with the stopper ring 54ms moving insliding contact with the rear inner peripheral surface 22qs of the guidesleeve 22s.

When the rear end of the spline shaft part 52b of the screw rod 52contacts the bottom surface 56e (see FIG. 16) of the rear end of thespline part 56b of the ratchet 56, the movement of the stopper ring 54msis completed.

Then, the screw rod 52 is screwed on the piston rod 54s to shorten thetotal length of the screw rod 52 and the piston rod 54s by rotating theoperation knob 50 reversely. In a normal operation, the screw rod 52cannot be rotated reversely; however, at this time, the release button40 is pressed deep to allow its reverse rotation, similarly to the firstembodiment. Because the stopper ring 54ms prevents the piston rod 54sfrom moving axially, the screw rod 52 is moved forward by rotating theoperation knob 50 reversely.

After the screw rod 52 is screwed on the piston rod 54s completely,similarly to the first embodiment, the operation knob 34 is rotatedreversely to return the movable section 30 to the ampule insertionposition, and then the ampule 70 is removed from the injection apparatus10s.

According to the injection apparatus 10s of the second embodiment, whenan injection amount is set, the screw rod 52 is fed rearward.Accordingly, the injection amount can be ascertained by the feedingamount of the screw rod 52, namely, that of the operation knob 50, inaddition to the numerical display shown by the indicator 61.

The present invention is not limited to the above-described embodiment,but may be embodied in various other modes. For example, the drivingmeans for moving the movable section relative to the body section may beconstituted by a rack and a pinion.

It is claimed:
 1. An injection apparatus, comprising an ampule having apiston for sealing an agent in a syringe, comprising:piston rod meansfor pressing the piston of the ampule in an axial direction; an ampuleholding part having an ampule insertion outer opening, having anoriginal circumference, which opening is expanded circumferentially whenthe ampule is inserted into the opening and having an ampule insertionspace for inserting the ampule thereinto, wherein the outer opening isrestored to its original circumference after the ampule is inserted intothe ampule insertion space, so that the ampule is held by the ampuleholding part temporarily; and ampule gripping means for gripping theampule and preventing axial movement thereof.
 2. The injection apparatusaccording to claim 1, wherein the ampule holding part has a pair ofampule-gripping elastic blades for securing the inserted ampuletherebetween; the opening is defined between side edges of the pair ofampule-gripping elastic blades and between front edges thereof; theampule insertion space is defined by an inner peripheral surface of thepair of ampule-gripping elastic blades; and the distance between theside edges of the pair of ampule-gripping elastic blades is shorter thanan outer diameter of the syringe of the ampule.
 3. The injectionapparatus according to claim 1, which further comprises a body sectionwhich abuts the ampule and which contains the piston rod means and amovable section having the ampule holding part, wherein the body sectionand the movable section have driving means that allows the body sectionand the movable section to move relative to each other between an ampuleinsertion position at which the ampule is inserted into the ampuleholding part of the movable section and a setting position at which themovable section is closest to the body section.
 4. The injectionapparatus according to claim 3, wherein the driving means comprisesscrew feeding means which has a guide screw shaft on the body sectionand a nut-type operation knob mounted on the movable section such thatthe operation knob is unmovable in the axial direction thereof,rotateable, and screws on a periphery of the guide screw shaft.
 5. Theinjection apparatus according to claim 3, wherein the ampule has aflange, and wherein the ampule-gripping means comprises:a flangehold-down part formed at a predetermined position of the ampuleinsertion space of the movable section, contacting a front surface ofthe flange of the inserted ampule, and moving the ampule rearward bypressing the front surface of the flange of the ampule when the movablesection moves to the setting position, and a flange pressing part whichis provided on the body section around the piston rod means and which ispressed against a rear surface of the flange of the ampule when themovable section and the body section are set at the setting position. 6.The injection apparatus according to claim 5, wherein the flangepressing part comprises:a spacer which freely engages the periphery ofthe piston rod means, and which is placed at a predetermined position ofthe ampule insertion space when the movable section is located at theampule insertion position so that the spacer substantially contacts therear surface of the flange of the ampule; and an elastic O-ring providedat a predetermined position of the periphery of the piston road meanssuch that the elastic O-ring is axially unmovable and pressed against arear surface of the spacer when the movable section is located at thesetting position.
 7. The injection apparatus according to claim 3,wherein the piston rod means comprises:a guide sleeve which is fixed tothe body section, projects forward from the body section, is concentricwith the inserted ampule, and has an outer diameter generally equal toan inner diameter of the syringe of the ampule; a piston rod which isinserted into the guide sleeve such that the piston road isnonrotateable with respect to the guide sleeve and axially slideable,and which has a screw hole; and a screw rod which has a screw part,formed at a front end thereof, and screwing on a screw part in a form ofa screw hole of the piston rod, and which has an operation knob formedat a rear end thereof, wherein the screw rod is movable together withthe piston rod between an initial position and a pushing-in position. 8.The injection apparatus according to claim 7, wherein the piston rodmeans further comprises rotation regulation means for regulating therotational direction of the screw rod in one direction.
 9. The injectionapparatus according to claim 8, which further comprises:detection meansfor detecting the rotational amount of the screw rod of the piston rodmeans and detecting a return of the screw rod from the pushing-inposition to the initial position; display means for displaying theinjection amount in correspondence to the rotational amount of the screwrod of the piston rod means after the screw rod returns to the initialposition; and a rotation regulation release means for releasing therotation regulation means of the piston rod means when the ampule isremoved from the ampule insertion space.
 10. The injection apparatusaccording to claim 7, wherein a concave part is formed on a peripheralsurface of the piston rod, wherein the concave part comprises a bottomsurface generally parallel with an inner peripheral surface of the guidesleeve, a front step surface being provided on a front side of thebottom surface and extending from the bottom surface outwardly in aradial direction of the piston rod, and a rear step surface beingprovided on a rear side of the bottom surface and extending from thebottom surface outwardly in the radial direction of the piston rod, andwherein the piston rod means further comprises:spring means forautomatically returning the screw rod and the piston rod to the initialposition when a force for pushing in the screw rod and the piston rod isreleased, and a stopper member which is positioned in the concave of thepiston rod, slides in contact with the bottom surface of the piston rodand the inner peripheral surface of the guide sleeve with apredetermined frictional force, moves together with the piston rod withthe stopper member in contact with the rear step surface of the pistonrod when the piston rod is pushed in, and stops the movement of thepiston rod with the stopper member in contact with the front stepsurface of the piston rod when the piston rod is returned by the springmeans, wherein a frictional force between the stopper member and thebottom surface of the piston rod is smaller than an automatic returnforce of the spring means; and a frictional force between the stoppermember and the inner peripheral surface of the guide sleeve is greaterthan the automatic return force of the spring means.
 11. The injectionapparatus according to claim 8, wherein a concave part is formed aperipheral surface of the piston rod, wherein the concave part comprisesa bottom surface generally parallel with an inner peripheral surface ofthe guide sleeve, a front step surface being provided on a front side ofthe bottom surface and extending from the bottom surface outwardly in aradial direction of the piston rod, and a rear step surface beingprovided on a rear side of the bottom surface and extending from thebottom surface outwardly in the radial direction of the piston rod, andwherein the piston rod means further comprises:spring means forautomatically returning the screw rod and the piston rod to the initialposition when a force for pushing in the screw rod and the piston rod isreleased, and a stopper member which is positioned in the concave of thepiston rod, slides in contact with the bottom surface of the piston rodand the inner peripheral surface of the guide sleeve with apredetermined frictional force, moves together with the piston rod withthe stopper member in contact with the rear step surface of the pistonrod when the piston rod is pushed in, and stops the movement of thepiston rod with the stopper member in contact with the front stepsurface of the piston rod when the piston rod is returned by the springmeans, wherein a frictional force between the stopper member and thebottom surface of the piston rod is smaller than an automatic returnforce of the spring means; and a frictional force between the stoppermember and the inner peripheral surface of the guide sleeve is greaterthan the automatic return force of the spring means.
 12. The injectionapparatus according to claim 9, wherein a concave part is formed on aperipheral surface of the piston rod, wherein the concave part comprisesa bottom surface generally parallel with an inner peripheral surface ofthe guide sleeve, a front step surface being provided on a front side ofthe bottom surface and extending from the bottom surface outwardly in aradial direction of the piston rod, and a rear step surface beingprovided on a rear side of the bottom surface and extending from thebottom surface outwardly in the radial direction of the piston rod, andwherein the piston rod means further comprises:spring means forautomatically returning the screw rod and the piston rod to the initialposition when a force for pushing in the screw rod and the piston rod isreleased, and a stopper member which is positioned in the concave of thepiston rod, slides in contact with the bottom surface of the piston rodand the inner peripheral surface of the guide sleeve with apredetermined frictional force, moves together with the piston rod withthe stopper member in contact with the rear step surface of the pistonrod when the piston rod is pushed in, and stops the movement of thepiston rod with the stopper member in contact with the front stepsurface of the piston rod when the piston rod is returned by the springmeans, wherein a frictional force between the stopper member and thebottom surface of the piston rod is smaller than an automatic returnforce of the spring means; and a frictional force between the stoppermember and the inner peripheral surface of the guide sleeve is greaterthan the automatic return force of the spring means.
 13. The injectionapparatus according to claim 10, wherein the stopper member is made of africtional/elastic material such as a rubber, wherein the front stepsurface of the piston rod is an inclined surface which extends from thebottom surface outwardly in the radial direction and towards a frontside of the piston rod, and wherein a wedge-shaped space is formedbetween the inclined surface and the inner peripheral surface of theguide sleeve.
 14. The injection apparatus according to claim 11, whereinthe stopper member is made of a frictional/elastic material such as arubber, wherein the front step surface of the piston rod is an inclinedsurface which extends from the bottom surface outwardly in the radialdirection and towards a front side of the piston rod, and wherein awedge-shaped space is formed between the inclined surface and the innerperipheral surface of the guide sleeve.
 15. The injection apparatusaccording to claim 12, wherein the stopper member is made of africtional/elastic material such as a rubber, wherein the front stepsurface of the piston rod is an inclined surface which extends from thebottom surface outwardly in the radial direction and towards a frontside of the piston rod, and wherein a wedge-shaped space is formedbetween the inclined surface and the inner peripheral surface of theguide sleeve.
 16. The injection apparatus according to claim 10, whereina stroke of the stopper member moving between the front step surface ofthe piston rod and the rear step surface thereof is smaller than theamount of the screw rod which is fed relative to the piston rod byrotating the screw rod to set a dosage amount for injection.
 17. Theinjection apparatus according to claim 11, wherein a stroke of thestopper member moving between the front step surface of the piston rodand the rear step surface thereof is smaller than the amount of thescrew rod which is fed relative to the piston rod by rotating the screwrod to set a dosage amount for injection.
 18. The injection apparatusaccording to claim 12, wherein a stroke of the stopper member movingbetween the front step surface of the piston rod and the rear stepsurface thereof is smaller than the amount of the screw rod which is fedrelative to the piston rod by rotating the screw rod to set a dosageamount for injection.
 19. The injection apparatus according to claim 10,wherein the concave is formed as a circumferential concave, and thestopper member is a ring-shaped stopper member provided on thecircumferential concave.
 20. The injection apparatus according to claim11, wherein the concave is formed as a circumferential concave, and thestopper member is a ring-shaped stopper member provided on thecircumferential concave.
 21. The injection apparatus according to claim12, wherein the concave is formed as a circumferential concave, and thestopper member is a ring-shaped stopper member provided on thecircumferential concave.